The present invention relates to a socket for an incandescent lamp in the shape of a straight tube, which is typically used for decorative illumination or general illumination. The invention also relates to a socket device using said socket.
Background of the Invention
Examples of well-known conventional straight tube type incandescent lamp used for decorative illumination or general illumination include a small incandescent lamp wherein a filament is installed in a cylindrical glass tube that has a flat sealing portion at each end; a pair of lead wires are respectively connected to both ends of the filament and are projected from the respective sealing portions at both ends of the glass tube to the outside of the glass tube; and wherein lead portions are formed by bending the projected portion of each lead wire into the shape of the letter U extending virtually parallel to the flat portion of the corresponding sealing portion. An incandescent lamp described above has no caps so that the lead portion of each lead wire functions as an electrical connection portion.
An example of sockets for an incandescent lamp structured as above is disclosed in Japanese Utility Model No. 1427197, which calls for mechanically supporting and electrically connecting an incandescent lamp by providing a socket body or a similar member with a pair of hooking terminals disposed opposite each other, and hooking the lead portions at both ends of the incandescent lamp to the respective hooking terminals, thereby disposing the incandescent lamp between the two hooking terminals.
However, a socket described above is not capable of providing reliable mechanical and electrical connection of the incandescent lamp, because the connecting operation is done simply by hooking the lead portions of the incandescent lamp to the hooking terminals. Furthermore, when attaching or removing the incandescent lamp, it is necessary to hook or unhook the lead portions while elastically deforming the hooking terminals. In other words, mounting and dismounting cannot be easily done according to the above configuration.
Other well-known examples of sockets include those described in Japanese Patent Laid-open No. 225482/1988 and Japanese Utility Model Laid-open Nos. 4086/1987, 193686/1986 and 85840/1986, although they all involve a lamp having a cap at each end, which is a lamp of a different type from the one related to the configuration described above, i. e. a capless type incandescent lamp. The aforementioned patent public disclosure and utility model public disclosures provide a structure of a socket which calls for inserting an electrical connector portion, which is in the shape of a plate or a bar and projects from a cap, between a pair of terminal pieces of a lamp contact terminal disposed in a socket, so that said electrical connector portion is mechanically supported between the two terminal pieces and electrically connected to the same.
In the above configuration of a socket, the lamp contact terminals through which electrical current flows are disposed deep inside the socket in order to prevent them from being inadvertently exposed to the outside of the socket. Therefore, when inserting an electrical connector portion of a cap of the lamp from the outside of the socket for electrical connection, it is difficult to set the insertion position between the pair of terminal pieces of the lamp contact terminal disposed in the inner part of the socket interior. In short, the above configuration is not convenient to connect an electrical connector portion to a lamp contact terminal. Especially in cases where a socket having such a structure is used for an incandescent lamp of the capless type described above, the incapability of setting an insertion position often causes the incandescent lamp to be displaced in the axial direction with respect to the socket, which may result in various problems, for example, causing a sealing portion to abut against a lamp contact terminal and prevent insertion of the lamp or to be accidentally inserted between the pair of terminal pieces of the lamp contact terminal.
In order to solve the above problems, an object of the present invention is to provide a socket and a socket device using said socket wherein mechanical and electrical connection of a capless type incandescent lamp to the socket can be executed easily and reliably, and wherein an insertion position of each lead portion of the incandescent lamp with respect to a lamp contact terminal disposed in the socket can be easily set when the incandescent lamp is inserted and connected to the socket, so that the lead portions of the incandescent lamp can be reliably connected to the lamp contact terminals and that the incandescent lamp can be connected to the socket at a position fixed with respect to the axial direction of the lamp tube.